Sources of intense, sub-microsecond x-ray pulses are required for testing the response of components and materials to pulsed fusion reactions. Desired pulse widths for such testing range from the order of 10 ns to several ms. Desired x-ray spectra peak in the range of about 1 to 5 MeV. Desired dose rates may range from 10.sup.10 to 10.sup.13 rads/sec. It is also desirable that the x-ray sources be transportable.
At the present time Blumlien driven diodes are used for high intensity ns pulsed x-ray sources. Such sources produce x-ray bursts which are of the order of 100 ns long. This is a factor of about 5 longer than the shortest burst desirable for such testing. Furthermore, Blumlien driven diodes have slow repetition rates, limited transportability, high cost, and poor reliability
There have been proposals to make use of hot plasmas for the generation of x-rays as in R.A. Shatas, et al., U.S. Pat. No. 3,746,860, issued July 17, 1973 for Soft X-Ray Generator Assisted by Laser, and T.G. Roberts, et al., U.S. Pat. No. 3,969,628, issued July 13, 1976 for Intense Energetic Electron Assisted X-Ray Generator. These proposals use short-lived, hot, dense plasmas to generate x-ray pulses which may have time durations ranging from 100 ns to 1 ms. Desirably short x-ray pulses are not, however, obtainable with the Shatas, et al. and Roberts, et al. techniques.
It is known that one can produce relatively stable, hot plasmas of low density. Stable plasma configurations have been described by R.A. Dandl, U.S. Pat. No. 3,728,217, issued Aug. 17, 1973 for Bumpy Torus Plasma Confinement Device. Dandl describes a so-called ELMO Bumpy Torus with hot annular plasma rings, or annuli, surrounding the toroidal axis and symmetrically located with respect to the mid-plane of the torus. The electron temperature within the annulus may be raised to a few MeV in hydrogen plasmas having number densities of the order of 10.sup.12 -10.sup.14 atoms/cc. The hot plasma ring is kept from spreading in the direction along the toroidal axis by a magnetic mirror formed from an inhomogeneous magnetic field within the torus. It is known that the trapping effect of the inhomogeneous field is enhanced by local currents generated in the surrounding plasma, making low density plasmas quite stable. The hot electrons circulate around the ring with drift velocities of the order of 0.1c,c being the speed of light. Thus, if the hot plasma ring has a circumference of the order of 30 cm, an electron circulates around the ring in a time of the order of 10 ns.